Method of producing picker sticks



Dec. 21, 1965 w. R. EGBERT METHOD OF PRODUCING PICKER STICKS Original Filed Oct. 29, 1963 -INVENTOR. WILLIAM R. EGBERT ATTORNEY United States Patent Ofifice 3,224,478 Patented Dec. 21, 1965 3,224,478 METHOD OF PRODUCING PICKER STICKS William R. Egbert, Mohawk, N.Y., assignor to Lundstrom Laboratories, Inc., Herkimer, N.Y., a corporation of New York Original application Oct. 29, 1963, Ser. No. 320,257, now Patent No. 3,172,429. Divided and this application Jan. 26, 1965, Ser. No. 428,029

3 Claims. (01. 144-320) This application is a division of my copending application Serial No. 320,257, filed October 29, 1963, now Patent No. 3,172,429, which in turn is a continuation-inpart of my original application Serial No. 832,026, filed August 6, 1959, and now abandoned.

In the operation of looms, a shuttle carrying the weft thread is shot back and forth across the warp shed by pickers fitted on the free ends of sticks mounted for fast rocking movement at opposite sides of the shed. When the shuttle arrives at one side of the loom, the picker stick at that side is rocked on a pivot at its butt end with a fast whipping motion which throws the shuttle at high speed back across the loom to the picker at the other side of the loom.

In order to achieve a required combination of whip and endurance, picker sticks are usually machined from blanks of a resilient natural wood such as hickory. Some picker sticks have been made of layers of plywood impregnated and bound together under heat and pressure by a thermosetting synthetic resin, in order to obtain better strength and wearing qualities in the sticks; but such sticks as heretofore made have been relatively expensive, and they do not possess the resilience or whip on looms which is provided by natural hickory picker sticks and is important to the successful operation of looms at very high picker speeds.

It has been proposed to improve the wear resistance of picker sticks while preserving the required resilience and shock resistance, by forming wooden blanks with oversized portions or bosses on their edges at the principal zones of wear and, through a process of wood densification, compressing the bosses into the main body of the wood so as to densify and harden each stick locally where it otherwise would soon wear away. Experience has shown, however, that picker sticks made in that way suffer localized overstressings of the wood fibers, which aifect the strength of the wood and often lead to warping of the sticks and to splintering or breaking of the sticks in loom service.

It is a principal object of this invention to provide new and improved Wooden picker sticks which will perform reliably and withstand the wear and shocks imposed upon them in loom service for much longer periods than usual wooden picker sticks.

Another object is to provide wooden picker sticks which are considerably enhanced in strength as well as in wear resistance and which still possess the properties of whip or resilience required for good performance on a loom.

A further object of the invention is to provide a manner of production of picker sticks by which in a single forming operation wooden blanks not only are increased in strength and wear resistance and kept resilient but also are brought to the final thickness desired in the finished sticks, thus enabling the elimination of a difiicult and expensive machining operation heretofore required for the finishing of picker sticks.

Still another object is to provide wooden picker sticks which do not warp on long exposure to atmospheric moisture.

According to the present invention, there is provided a picker stick construction wherein an elongated unitary body of wood composed essentially of the integrated fibers and lignin of a piece or blank of natural hardwood to be formed into the picker stick is compressed and densified from opposite sides thereof over most, or more advantageously all, of its length so as to be composed in and evenly along outer zones of the long body of densified yet still integrated natural fibers and lignin having a density and hardness substantially greater than that of the natural hardwood, and yet wherein the densification is so limited that the body continues to have a relatively undensified core or central zone lying between the densified outer zones and extending throughout at least the length of the relatively long intermediate portion of the body between the picker end portion and the butt end portion thereof, in which core the density and hardness of the wood at any location therealong is less and the resilience thereof is greater than that of the contiguous wood in said outer zones.

Further, the densified outer zones of the hardwood body are formed with sealed toughened facial layers constituted by a hardening and sealing agent, such, for

7 example, as a suitable resin-forming composition, having been applied to the opposite sides of the body prior to their being compressed and densified. These layers stabilize the densified outer zones, making the picker stick highly resistant to warping and other changes of its properties.

I have found that picker sticks made to embody such a construction have an extraordinarily valuable combinaation of properties. Not only their wear resistance but also their strength, their stability and their service life are greatly enhanced, and yet they also exhibit qualities of resilience and whip, together with a limited weight, which suit them excellently for the exacting performance requirements of modern high speed loom operations.

The picker end portion of each stick is advantageously compressed and densified throughout its thickness to an approximately uniform density and hardness at least as great as that produced in any of the other densified zones of the stick body. The wood of the other body portions may be compressed and densified along opposite sides thereof to possess hardnesses progressively increasing therealong from the butt end portion to the picker end portion of the stick, yet in a central zone or core along the body this Wood is kept less densified and hence more resilient or flexible than the contiguous wood near the surfaces of the compressed sides.

The production of picker sticks embodying the construction of this invention is readily carried out by subjecting oversized wooden blanks after a suitable pretreatment of each blank to a tapering compression between heated platens which deform the blanks into densified bodies tapering in thickness from end to end thereof, with the least thickness at the picker end, and limiting the compression so that when the picker end portion and outer zones of the other body portions of each blank have attained the desired degrees of increased density and hardness there will still be a core or central zone of more resilient wood extending throughout the long intermediate portion and the butt end portion of the densified body. By the single compression operation the opposite sides or faces of each of the blanks can be brought to the form and also to the surface finish desired in the finished picker sticks, so that no machining operation will be required on either of these faces in order to complete the final shaping and finishing of the sticks.

The blanks used are preferably made of natural wood that is highly resilient, such as well cured hickory wood or other suitable natural hardwood.

Other objects, features and advantages of the invention and preferred ways of practicing it will be apparent from the following detailed description of an illustrative embodiment. The detailed description refers to the accompanying drawing in which:

FIG. 1 is a perspective view, partially broken away, of a finished picker stick constructed according to the invention;

FIG. 2 is a similar perspective view of a compressed picker stick blank before conversion into the finished stick, the stipling on this figure indicating different conditions of density and hardness of the wood;

FIG. 3 is a schematic view in side elevation of a raw wooden blank positioned alongside a die between press platens in readiness for compression of the blank; and

FIG. 4 is a view similar to FIG. 3 showing the relationship of the blank, the die and the platens at the end of the compression operation.

In FIG. 1 of the drawing there is shown a finished wooden picker stick 10 made according to this invention which corresponds in its major dimensions to the picker sticks widely used on certain commercial looms. The stick shown is formed with its body compressed and tapered evenly in thickness between its opposite sides or faces 11 and 12, over its entire length from the base 14 of its butt end portion 15 to a point of least thickness at the tip 19 of its picker end portion 18. The greatest extent of compression, density and hardness is provided in the wood of the picker end portion 18. The wood of the butt end portion 15 and intermediate portion 16 of the stick body, i.e., of the long body portion extending away from the picker end portion, is compressed and densified along opposite sides thereof to a limited extent so as to possess in outer zones thereof along these sides an increased density and hardness which at any location therealong is substantially greater than the density and hardness of the wood in a core or central zone of the body lying between the densified outer bones.

The finished stick 10 of FIG. 1 is machined from a compressed blank such as shown at 10A in FIG. 2. The compressed blank in turn is formed from a raw blank such as seen at 10B in FIG. 3 of the drawing. The varied conditions of compression, density and hardness provided along the body of the stick are represented diagrammatically by the stipling applied in FIG. 2 to the front edge 20 of the compressed blank 10A.

In the illustrative stick 10 and blank 10A here shown, the wood of the picker end portion 18 is compressed and densified throughout its thickness to a hardness substantially greater than that of the natural hardwood blank formed into the stick body. The wood in outer zones of the body near the side surfaces of intermediate portion 16 is compressed and densified to a hardness less than that of portion 18 but greater than that of the wood of the butt end portion 15. The wood of the butt end portion is somewhat compressed and densified near its side surfaces but is kept substantially entirely uncompressed in a central zone 17 between its opposite sides. At any point along the stick body from the butt end portion 15 through the intermediate portion 16, the density and hardness of the wood near the surfaces of the compressed sides is greater than'that of the wood in the central zone of the body between those sides.

The varied conditions of compression, density and hardness provided in the several portions of the illustrative picker stick may be further indicated by reference to illustrative hardness measurements made at typical points in outer zones and in the central zone of each of the body portions 15, 16 and 18. See FIG. 2. At a central point 150 of the butt end portion 15, the wood has substantially the same density and hardness as the original wood used to make the raw blank 10B. In the use of natural hickory wood, the hardness at point 15c amounts, for example, to approximately 75 Shore Durometer units, plus or minus units, as determined by tests with a Shore Durometer, Type D, produced by the Shore Instrument Manufacturing Company of Jamaica, New York. At points 1511' and 15b in outer zones near 4 the opposite side surfaces of portion 15, the wood has a somewhat greater density manifested by a hardness read-'- ing, for example, of approximately Shore units. In: the intermediate portion of the body, the wood in the outer zones as at points 16a and 16b is quite materially/ increased in density to a hardness reading, for example,

of approximately 86 Shore units; while in the central zone at point 160 the hardness is less than at the outer points but still is greater than in the central zone of the butt end portion, being, for example, approximately 84 Shore units. In the picker end portion 18, which is compressed and densified to an approximately uniform hardness throughout its thickness, the hardness reading amounts, for example, to approximately 90 Shore units at each of the points 18a, 18b and 18c.

An eflective manner of forming a wooden blank into the compressed blank of FIG. 2 is illustrated schematically in FIGS. 3 and 4 of the drawing. The raw blank 10B is cut from the'desired hardwood, such as hickory, to approximately the same length and width as required for the compressed blank 10A, and to a thickness greater than required for the compressed blank. Its thickness in the form shown is approximately uniform from end to end of the wooden body.

The blank 103 when ready to be compressed is placed in a press between heated platens 30 and 32 which are capable of applying to the blank a'high pressure of the order, for example, of 1500 pounds per square inch. The blank is laid on the lower platen 32 alongside an incompressible die 34 serving as a stop to limit the convergence of the two platens. There are similar dies or stops at either side of the blank, each tapered to correspond to the dimensions and taper desired in the thickness of the firtished picker stick. I

Before being placed in the press, the blank 10B is suit-- ably heated in order to pre-plasticize lignin contained in the wood, such as by treating it with live steam or hot air. Thi treatment advantageously is preceded, accompanied or followed by the application of a resin-forming solution to at least the opposite side faces of the blank, such as a solution which at the elevated temperature of the press platens will form in pores of the wood a thermoset resin such as a urea-formaldehyde resin, a melamine resin, or the like. Thus under the heat and pressure of the press platens a desirable dense, smooth and tough impregnated surface, which seals the pores of the wood against moisture absorption and inhibits the natural tendency of picker sticks to warp, is formed on the compressed sides of the blank. For the latter purpose, the blank may be coated on both of its faces with an aqueous solution of the character described in U.S. Patent No. 2,567,292 to Carl Brynolf Lundstrom.

Having been suitably pre-trea-ted and placed in the press as indicated in FIG. 3, the blank 10B is subjected to compression between the plattens 30 and 32, while being heated by the plattens, until the plattens have closed against the die 34 as seen in FIG. 4. As the compression of the blank proceeds, the plattens become tilted, one relative to the other, by their coaction against the faces of the blank and the die. In a typical operation, for example, the plattens are heated to a temperature of approximately 300 F. and are pressed together against the blank and die under a pressure of approximately 1500 pounds: per square inch for a period of approximately 40 min-- utes. After the plattens have closed against the die, they' are held closed under pressure and cooled to a temperature of F. or below to set the displaced lignin and fibers in the compressed blank so that the product will remain permanently in the densified and hardened form shown in FIG.v 2.

The compressed blank 10A is then in a condition suitable for relatively inexpensive conversion into the finished picker stick 10. Thi conversion may be effected, for example, by machining the butt end portion 15 to the desired end contour seen at 14 in FIG. 1; machining along the front and back edges 26 and 21 to give the stick the desired final width and the desired tapered edge 21a along the picker end portion; drilling an opening 24 through the butt end to be fitted with a bushing and a loom mounting pivot; and drilling openings 25 and 26 through the central zone of the butt end at either side of the pivot opening to receive butt reinforcing bolts.

A typical finished picker stick made according to this invention has, for example, a length of 34 /2 inches, 21 width of 1 /8 inches which at the picker end portion is tapered down to a tip width of 1 inch, and a thickness tapering evenly from 4; inch at the base of the butt end to /8 inch at the tip of the picker end. The uncom pressed blank used for the production of such a stick has, for example, a length of 35 inches, a width of 2 inches and a thickness of inch. After the compression operation, the length and the width of the blank remain approximately the same but its thickness is reduced to the final values present in the finished stick, i.e., its thickness tapers evenly from A; inch at the base of the butt end to inch at the tip of the picker end.

It will be understood, of course, that the dimensions, the values of hardness measurements and other details of the illustrative embodiment as set forth herein are subject to Wide variations, depending upon the desired size and other desired qualities of the finished picker sticks. For example, when it is desired that the stick have a greater mass in the butt end and intermediate portions, the uncompressed blank is cut on a taper so as to have a greater thickness at the base of the butt end and to decrease in thickness evenly to its other end; in which case the upper platen 30 of the press assumes a tilted position relative to the lower platen at the outset of the compression and the compressed outer zones of the densified blank are more nearly uniform in density and hardness over their length.

I claim:

1. The method of producing a picker stick, which comprises forming an elongated unitary blank composed essentially of the integrated fibers and lignin of a natural hardwood and having a length and width at least equal to the length and width of the desired picker stick, the thickness of said blank at substantially every point along its length being greater than desired at the same point in the picker stick, subjecting said blank to heat suflicient to plasticize lignin contained in the wood and to compression between heated platens extending over the whole of and pressed together against the opposite side faces of the blank, so as to compress the blank on a taper and form it into a densified wooden body reduced and tapered in thickness from end to end thereof, as the compression proceeds allowing one of he platens to tilt relative to the other and yet limiting the tilting by engaging said one platen against incompressible stops disposed between portions of the platens at opposite sides of said blank, continuing the convergence of the platens until they are fully seated against said stops at a relative position of the platens in which the smaller end portion of said body has the thickness required to hold a loom picker and the wood of the blank has been plastically displaced and densified in outer zones thereof extending throughout the breadth and length of opposite sides thereof and yet a core having less hardness than said outer zones remains along the center of the body between said outer zones throughout at least the length thereof extending to said smaller end portion, and while maintaining the platens in s aid'position cooling said body under compression between them to reset the displaced lignin of the compressed wood.

2. The method of producing a picker stick, which comprises forming an elognated unitary blank of natural hickory wood having a length and width at least equal to the length and width of the desired picker stick, the thickness of said blank at substantially every point along its length being greater than desired at the same point in the picker stick, applying to at least the opposite side faces of said blank a resin solution which at an elevated temperature will form a thermoset resin in pores of the wood, subjecting the resin-coated blank to heat and to compression between heated platens extending over the whole of and pressed together against the opposite side faces of the blank so as to compress the blank on a taper and form it into a densified wooden body reduced and tapered to thickness from end to end thereof, as the compression proceeds allowing one of the platens to tilt relative to the other and yet limiting the tilting by engaging said one platen against incompressible stops disposed betwe n portions of the platens at opposite sides of said blank, continuing the convergence of the platens until they are fully seated against said stops at a relative position of the platens in which the smaller end portion of said body has the thickness required to hold a loom picker and the wood of the blank has been plastically displaced and densified in outer zones thereof extending throughout the breadth and length of opposite sides thereof and yet a core having less hardness than said outer zones remains between said zones along the center of the body through at least the length thereof extending to said smaller end ortion, and while maintaining the platens in said position cooling said body under compression between them to reset the displaced lignin of the compressed wood. 3. The method of producing a picker stick, which comprises forming an elongated unitary blank composed essentially of the integrated fibers of lignin of natural hickory wood and having a length and width at least equal to the length and width of the desired picker stick, the thickness of said blank at substantially every point along its length being greater than desired at the same point in the picker stick, subjecting said blank to heat sufiicient to plasticize lignin contained in the wood and to compression between heated platens extending over the whole of and pressed together against the opposite side faces of the blank so as to compress the blank on a taper and form it into a densifie-d wooden body reduced and tapered in thickness from end to end thereof, stopping the convergence of the platens by seating them against incompressible stops, at a relative position of the platens in which the smaller end portion of said body has the thickness required to hold a loom picker and the wood of the blank has been plastically displaced and densified in outer zones thereof extending throughout the breadth and length of opposite sides thereof and yet a core having less hardness than said outer zones remains along the center of the body between said outer zones throughout at least the length thereof extending to said smaller end portion, and while maintaining the platens in said position cooling said body under compression between them to reset the displaced lignin of the compressed Wood.

References ited by the Examiner UNITED STATES PATENTS 2,470,506 5/ 1949 Lundstrom 144327 X 2,666,463 1/1954 Heritage 144-320 FOREIGN PATENTS 286,059 5/1931 Italy. 991,362 6/1951 France.

WILLIAM W. DYER, JR., Primary Examiner.

\VAYMOND D. BRAY, Assistant Examiner. 

1. THE METHOD OF PRODUCING A PICKER STICK, WHICH COMPRISES FORMING AN ELONGATED UNITARY BLANK COMPOSED ESSENTIALLY OF THE INTEGRATED FIBERS AND LIGNIN OF A NATURAL HARDWOOD AND HAVING A LENGTH AND WIDTH AT LEAST EQUAL TO THE LENGTH AND WIDTH OF THE DESIRED PICKER STICK, THE THICKNESS OF SAID BLANK AT SUBSTANTIALLY EVERY POINT ALONG ITS LENGTH BEING GREATER THAN DESIRED AT THE SAME POINT IN THE PICKER STICK, SUBJECTING SAID BLANK TO HEAT SUFFICIENT TO PLASTICIZE LEGNIN CONTAINED IN THE WOOD AND TO COMPRESSION BETWEEN HEATED PLATENS EXTENDING OVER THE WHOLE OF AND PRESSED TOGETHER AGAINST THE OPPOSITE SIDE FACES OF THE BLANK, SO AS TO COMPRESS THE BLANK ON A TAPER AND FORM IT INTO A DENSIFIED WOODEN BODY REDUCED AND TAPERED IN THICKNESS FROM END TO END THEREOF, AS THE COMPRESSION PROCEEDS ALLOWING ONE OF THE PLATENS TO TILT RELATIVE TO THE OTHER AND YET LIMITING THE TILTING BY ENGAGING SAID ONE PLATEN AGAINST INCOMPRESSIBLE STOPS DISPOSED BETWEEN PORTIONS OF THGE PLATENS AT OPPOSITE SIDES OF SAID BLANK, CONTINUING THE CONVERGENCE OF THE PLATENS UNTIL THEY ARE FULLY SEATED AGAINST SAID STOPS AT A RELATIVE POSITION OF THE PLATENS IN WHICH THE SMALLER END PORTION OF SAID BODY HAS THE THICKNESS REQUIRED TO HOLD A LOOM PICKER AND THE WOOD OF THE BLANK HAS BEEN PLASTICALLY DISPLACED AND DENSIFIED IN OUTER ZONES THEREOF EXTENDING THROUGHOUT THE BREADTH AND LENGTH OF OPPOSITE SIDES THEREOF AND YET A CORE HAVING LESS HARDNESS THAN SAID OUTER ZONES REMAINS ALONG THE CENTER OF THE BODY BETWEEN SAID OUTER ZONES THROUGHOUT AT LEAST THE LENGTH THEREOF EXTENDING TO SAID SMALLER END PORTION, AND WHILE MAINTAINING THE PLATENS IN SAID POSITION COOLING SAID BODY UNDER COMPRESSION BETWEEN THEM TO RESET THE DISPLACED LIGNIN OF THE COMPRESSED WOOD. 